In alt.home.repair, on Fri, 23 Feb 2018 20:22:55 -0600, Terry Coombs
wrote:

On 2/23/2018 7:06 PM, ultred ragnusen wrote:
Oren wrote:

Surging engines often is because of improper air / fuel mixture.
Someone said it is likely surging due to clogged fuel passageways, which
makes sense because the air passageways aren't clogged.

If it's the clogged fuel passageways, it's likely because I don't start
these engines for months (sometimes years) at a time, where I leave the
fuel in them (sometimes I pour it out before use if it's really old).

But I wonder why it surges due to clogged fuel passageways?
* snipped

Something has to be VARIABLE for the surging to occur.

* That's the action of the governer . As the motor dies due to fuel
starvation the governer opens the throttle to bring it back up to speed
. The throttle must open far enough to run on the main jet , which
causes the motor to overspeed , causing the governer to close the
throttle to slow it down - right back into the fuel starvation zone
which causes the governer to open the throttle ... over and over and
over . As soon as you load it enough to run on the main jet it'll smooth
right out .

That's a great answer. I knew it related to the governor, but I didn't
know details. Do they still use a plastic leaf that catches the wind
that comes somehow from the spinning crankshaft? The leaf pulls in one
direction and a spring pulls it back and opens the throttle farther when
the engine slows and the wind is less.